DESCRIPTION (APPLICATION ABSTRACT): Diabetes medical errors affect 80 percent of adults with diabetes in the United States The leading cause of error is inappropriate or inadequate pharmacologic action that fails to achieve specific clinical aims. Diabetes medical errors lead to tens of thousands of preventable adverse events in the United States each year, and to $3.9 billion a year of potentially avoidable health care charges. This project evaluates in a randomized trial whether customized direct feedback of medical error information to diabetes patients and their physicians reduces diabetes medical error rates. Eighty primary care physicians and their 1,840 patients with diabetes medical errors (average of 23 patients with error per physician) will be block randomized to one of four study arms: (A) Customized feedback of medical error information to patient only. (B) Customized feedback of medical error information to physician only. (C) Customized feedback of medical error information to both the patient and the physician. (D) Control group with no intervention. The patient intervention and physician intervention are conceptually powerful yet simple and inexpensive interventions based on customization theory and on our previous work. We hypothesize that the combined intervention (C) will reduce error more than the other interventions (A or B) or the control. The unit of randomization and unit of analysis are primary care physicians. Because patients are nested within physicians, hierarchical logistic models (MLwiN) will be used to test all hypotheses. Propensity scores and standard covariate adjustment will be used to correct for selection effects across levels. Detailed economic analysis will establish the relationship between diabetes error and long-term costs, and the short-term cost to payers of interventions to reduce diabetes errors. This project will advance our understanding of the acceptability and effectiveness of "patient-direct" strategies to reduce medical error as recommended in the IOM report, "Crossing the Quality Chasm." The inexpensive customized intervention has potential to be widely disseminated and can be seamlessly integrated with other interventions to further reduce medical error. Results will be relevant to clinicians, payers, and policymakers.